There are image forming apparatuses that estimate the remaining amount of toner accommodated in toner cartridges. Various techniques for estimating the remaining amount of toner are examined. For example, there is a technique for calculating the remaining amount of toner based on the rotation time of toner supply motors. However, in the technique, estimation of the remaining amount of toner deviates in accordance with a decrease in the remaining amount of toner accommodated in a toner cartridge in some cases.